1. Field of Invention
Apparatuses and methods consistent with the present invention relate to a light source driving apparatus, a light source driving method and a display apparatus, and more particularly, to an apparatus for driving a light source used as a backlight while displaying an image and adjusting light quantity thereof, a method thereof, and a display apparatus having the light source driving apparatus.
2. Description of the Related Art
A display apparatus such as a liquid crystal display (LCD) television, etc. is provided with a light source that is used as a backlight while displaying an image and achieved by a light emitting diode (LED) or the like. Such a display apparatus includes a light source driving circuit to drive the light source, and the light source driving circuit controls an electric current supplied to the light source so that the light source can emit light of desired quantity.
As a method for adjusting the light quantity of the light source, i.e., as a dimming method, there are a pulse width modulation (PWM) dimming method that adjusts a duty ratio of an electric current to be supplied to the light source, an analog dimming method that adjusts a peak value of the current, etc. In particular, the analog dimming method is relatively superior in efficiency and heat-generation characteristics to the PWM dimming method.
Meanwhile, the light source driving circuit includes a linear type circuit and a switching type circuit. The switching-type light source driving circuit has been widely used since it has a relatively high efficiency. FIG. 1 shows a conventional switching-type light source driving circuit. In FIG. 1, a reference numeral of 1 indicates a light source, a reference numeral of 2 indicates a light source driving circuit, and a reference numeral of 3 indicates a power source. As shown in FIG. 1, the light source driving circuit 2 includes a switching device 31 realized by a metal oxide semiconductor field effect transistor (MOSFET) or the like; an inductor 32, a diode 33, a capacitor 24, a resistor 25, and a PWM controller 26.
However, the conventional light source driving circuit 2 has to have a reactive device such as the inductor 22 and the capacitor 24 since it is the switching type. Accordingly, there is a problem of a slow response because decrease of an output current Io relies on natural discharge of energy stored in the reactive device when to decrease the output current Io.
For example, in the case where the analog dimming method is applied to the light source driving circuit 2, as shown in FIG. 2, the current Io flowing in the light source 1 in response to a square-wave analog dimming signal has a considerably long response delay d in a falling edge.